Adverse drug events have been documented as a significant problem in inpatient psychiatric facilities, but methods of preventing errors in this setting have not been researched. This study, conducted at an academic inpatient psychiatric hospital, combined a computerized provider order entry system with a structured event reporting system that was used by physicians, nurses, and pharmacists. Implementation of the system was associated with a significant reduction in both prescribing errors and medication administration errors over a 5-year period.